JP2015074192A - Release film for anisotropic electrically conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film for an anisotropic electrically conductive film, which can allow the peel force between the anisotropic electrically conductive film and a carrier film to be restrained from being fluctuated after a temporarily sticking step and allow the carrier film to be peeled stably at a carrier film peeling step before a normally sticking step.SOLUTION: The release film for the anisotropic electrically conductive film has such a release layer on at least one surface of a base material film that the plastic deformation hardness of the surface of the release layer is 20 mgf/μmor higher and the elastic deformation hardness thereof is 400 mgf/μmor higher when the plastic deformation hardness is measured by a micro hardness meter.

Description

  The present invention relates to a release film that can be suitably used as a protective sheet (carrier film and separator) for an anisotropic conductive film (ACF) used as, for example, a circuit connection material for a display.

  In recent years, with the spread of liquid crystal display devices (LCD) and the like, the demand for anisotropic conductive films (ACF) is rapidly increasing. Anisotropic conductive film has adhesiveness, and is used for electrical connection of members used in LCDs in particular. After bonding, it exhibits conductivity in the thickness direction and insulation in the surface direction. It is the material to show (patent documents 1-5).

  Since the anisotropic conductive film has adhesiveness, it is usually stored in a state protected by a release film. The release film is preferably imparted with antistatic properties. That is, since the anisotropic conductive film is used, for example, for joining the flexible substrate and the LCD, the release film has an antistatic property, so that foreign matter is caught or adhered when the anisotropic conductive film is attached. This is because the anisotropic conductive film itself is charged by the charge generated when the release film is peeled off, and the film vibrates at the time of sticking, preventing sticking problems. is there.

  An anisotropic conductive film is usually electrically conductive in an insulating adhesive varnish obtained by mixing an insulating resin such as an epoxy resin (see, for example, Patent Documents 2 to 4) with a coupling agent, a curing agent, a curing accelerator, and the like. The conductive particles are mixed and dispersed to form a conductive adhesive varnish, which is coated and dried on a release film as a carrier film to form an anisotropic conductive film. The anisotropic conductive film surface may be further multilayered by applying an insulating adhesive varnish not containing conductive particles. There is also a method in which an insulating adhesive varnish that does not contain conductive particles is applied on a carrier film, and then the conductive particles are sprayed onto a layer made of such an insulating adhesive varnish. In such production, since heat is usually applied at 60 ° C. to 150 ° C. for 1 minute to 30 minutes in the drying step, a polyester film is often used as the base material of the carrier film.

Examples of the use of anisotropic conductive films include connection of ITO terminals on a glass substrate of a liquid crystal panel, connection of terminals of a flexible substrate or TCP (Tape Carrier package), connection of a semiconductor chip on a motherboard, etc. Can be mentioned. More specifically, in general, after bonding an anisotropic conductive film to one of the objects to be bonded, temporary bonding (see, for example, Patent Document 5) under arbitrary temperature and pressure conditions, The carrier film is peeled off, the other of the objects to be bonded is bonded to the carrier film, and the temperature and pressure are applied again to perform the main bonding. Here, the temporary bonding conditions are, for example, a temperature of 60 to 100 ° C. for 1 to 5 seconds and a pressure of about 1 to 5 MPa, and the bonding conditions are, for example, a temperature of 100 to 250 ° C. for 0 to 10 seconds and a pressure of about 1 to 60 MPa. It is.
On the other hand, as a release film having antistatic properties, there are reports such as Patent Documents 6 and 7, for example.

JP 2001-171033 A JP 2005-307210 A JP 2010-174228 A JP 2010-261003 A JP 2012-69255 A Japanese Patent Laid-Open No. 5-16309 JP 2007-90817 A

In the temporary bonding step when using the anisotropic conductive film described above, the carrier film does not increase even if temporarily bonded to the carrier film so that the carrier film can be easily peeled in the subsequent main bonding step. However, according to the study by the present inventors, for example, a conventional release film as disclosed in Patent Documents 6 and 7, for example, a conventional curable silicone resin type release film is used as a carrier. When used as a film, it was found that even if the peeling force at room temperature was controlled, the peeling force fluctuated due to a temperature change after the temporary bonding step, and peeling failure might occur. It has also been found that such a phenomenon is likely to occur particularly in an epoxy anisotropic conductive film.
Then, an object of this invention is to provide the release film in which the fluctuation | variation of peeling force was suppressed after the temporary adhesion process at the time of use of an anisotropic conductive film.

  As a result of intensive investigations to solve such problems, the present inventors have found that the characteristics relating to the hardness of the surface of the release layer, not the type of material constituting the release layer, show the temperature change after the temporary bonding step. The present inventors have found that there is an effect of suppressing fluctuations in peeling force due to the present invention and have completed the present invention.

Thus, according to the present invention,
1. A release film having a release layer on at least one surface of a base film, the plastic deformation hardness obtained by a microhardness meter on the release layer surface is 20 mgf / μm ² or more, and the elastic deformation hardness is 400 mgf / μm. ^A release film for anisotropic conductive film, which is ² or more.
2. 2. The release film for anisotropic conductive film according to 1 above, wherein the release layer is a silicon oxide film formed by hydrolysis and / or condensation reaction of a tetrafunctional silicon compound.
3. The release film for anisotropic conductive films according to 1 or 2 above, wherein the surface resistivity on the surface of the release layer is 10 ⁵ to 10 ¹¹ Ω / □.
Is provided.

  In the release film of the present invention, when the anisotropic conductive film is used, the fluctuation of the peeling force between the anisotropic conductive film and the carrier film due to the temperature change after the temporary bonding process is suppressed. Peeling in the carrier film peeling step can be stably performed.

[Release film]
The release film for anisotropic conductive film of the present invention has a release layer on at least one side of a base film.

(Surface hardness)
The release film of the present invention needs to have a plastic deformation hardness of 20 mgf / μm ² or more determined by a microhardness meter on the surface of the release layer and an elastic deformation hardness of 400 mgf / μm ² or more. is there. By doing so, it is possible to suppress the peeling force fluctuation between the anisotropic conductive film and the carrier film due to the temperature change after the temporary bonding step. When at least one of the plastic deformation hardness and the elastic deformation hardness is too low, the peeling force after the temporary bonding process greatly varies depending on the temperature. From this point of view, the plastic deformation hardness is preferably 40 mgf / μm ² or more, more preferably 50 mgf / μm ² or more, particularly preferably 70 mgf / μm ² , and the elastic deformation hardness is preferably 450 mgf / μm. ² or more, more preferably 600 mgf / μm ² or more, particularly preferably 640 mgf / μm ² or more. On the other hand, from the viewpoint of fluctuations in the peel force after the temporary bonding step, it is preferable that the plastic deformation hardness and the elastic deformation hardness are high, and there is no particular upper limit, but if it is too hard, the release layer tends to break during handling. Due to the tendency, the plastic deformation hardness is preferably 150 mgf / μm ² or less, more preferably 100 mgf / μm ² or less, and the elastic deformation hardness is preferably 1000 mgf / μm ² or less, more preferably 800 mgf. / Μm ² or less.

  In order to achieve such surface hardness, it may be mentioned that the curing conditions are made stricter than usual. For example, a configuration of a preferable release layer to be described later may be adopted, and at the same time, a curing temperature during coating and drying may be set to 130 ° C. or more, and a curing time may be set to 20 seconds or more. Moreover, hardening may be accelerated | stimulated by off-annealing after coating at low temperature, and you may adjust with the thickness of a mold release layer.

(Peeling force)
The release film of the present invention has an ambient temperature peeling force of 10 to 10 after bonding an epoxy adhesive tape (Teraoka Seisakusho: No. 5150) to the release layer surface under the conditions of 100 ° C., 0.05 MPa, 30 seconds. The range is preferably 1000 g / 25 mm, more preferably 20 to 600 g / 25 mm, and still more preferably 100 to 500 g / 25 mm. When the room temperature peeling force is within this range, the peelability after the ACF temporary pressing step is excellent. When the room temperature peeling force is too high, it tends to be difficult to peel off after temporary pressure bonding. On the other hand, if it is too low, the anisotropic conductive film and the release film are naturally peeled off, and the handleability tends to decrease.

  Also, an epoxy adhesive tape (Teraoka Seisakusho: No. 5150) was bonded to the surface of the release layer under the conditions of 100 ° C., 0.05 MPa, 30 seconds, and then heated immediately after heating at 80 ° C. for 30 seconds on the heating plate. The peeling force is preferably 6 times or less of the room temperature peeling force and 100 g / 25 mm or more. If the heat peeling force is satisfied, the temperature dependency of the peeling force is small, so it is preferable for peeling in the pre-adhesion film peeling step after ACF temporary bonding, and the temporary bonding step when using an anisotropic conductive film. Subsequent fluctuations in the peeling force are less likely to occur, and it is possible to peel with a stable peeling force and to have appropriate adhesion to the anisotropic conductive film. From such a viewpoint, the peeling force during heating is more preferably 300 g / 25 mm or more, and most preferably 500 g / 25 mm or more. When the peeling force is too low, the anisotropic conductive film and the release film tend to be difficult to adhere to each other, and the anisotropic conductive film tends to be peeled easily in the use process, and partial floating tends to occur. There is a tendency. Further, the heat peeling force is more preferably 5.5 times or less, further preferably 3 times or less, particularly preferably 2 times or less, and most preferably 1.5 times or less than the room temperature peeling force. If the heating peel force is too high relative to the room temperature peel force, the peel force will fluctuate greatly due to temperature changes after the temporary bonding process, and the release film will be stably peeled off from the anisotropic conductive film after temporary bonding. Tend to be difficult and difficult to handle.

  Such peeling force can be adjusted by the type, thickness, additive, curing conditions, etc. of the release layer. In particular, in order to reduce the rate of change of the heat peeling force with respect to the room temperature peeling force, an embodiment that satisfies the hardness on the surface of the release layer defined by the present invention may be used.

(Antistatic property)
The release film of the present invention preferably has antistatic properties, and the surface specific resistance of the release layer surface is preferably 1 × 10 ⁵ to 1 × 10 ¹¹ Ω / □. By having such an antistatic property, peeling charging can be suppressed and adhesion of dust can be suppressed. When the surface specific resistance is too high, the effect of suppressing peeling charge tends to be low. On the other hand, if it is too low, when such a release layer falls off and mixes into the anisotropic conductive film, the mixed release layer imparts conductivity in the surface direction of the anisotropic conductive film. Therefore, there is a risk of causing a defect in which adjacent terminals to be insulated are electrically connected. In order to avoid this defect, it is preferable that the release layer has a surface resistivity of a certain value or more. From this viewpoint, it is more preferably 1 × 10 ⁶ Ω / □ or more, and further preferably 1 × 10 ⁷ Ω / □ or more. A method for achieving such surface resistance resistivity is not particularly limited, but can be achieved by adopting a preferred embodiment of a release layer to be described later, for example.

[Base film]
The base film in the present invention is not particularly limited as long as it does not hinder the object of the present invention and becomes the base of the release film, but is preferably a film made of a thermoplastic resin. Preferred examples of the thermoplastic resin include polyolefins such as polyethylene and polypropylene, polystyrene, acrylic, polyester, and polycarbonate. Among these, a polyester film is preferable from the viewpoint of excellent balance between mechanical properties, foreign matter, a small amount of impurities, cost, and the like.

  The polyester constituting the polyester film is preferably a polyester formed from dicarboxylic acid (or an ester-forming derivative thereof) and glycol (or an ester-forming derivative thereof). Such polyester may be substantially linear and has film-forming properties, particularly those having film-forming properties by melt molding. Examples of the dicarboxylic acid include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and anthracene dicarboxylic acid. Can be mentioned. Examples of glycols include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, diethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, etc., or 1,4-cyclohexanediethylene. Examples include alicyclic diols such as methanol. Among these polyesters, polyalkylene terephthalate and polyalkylene-2,6-naphthalate, particularly polyethylene terephthalate and polyethylene-2,6-naphthalate are preferable.

  These may contain 20 mol% or less of a copolymer component based on the total acid component. For example, 80 mol% or more of the total acid component may be a terephthalic acid component or a 2,6-naphthalenedicarboxylic acid component, and a copolymerized polyester in which 80 mol% or more of the total glycol component is an ethylene glycol component may be used. In that case, 20 mol% or less of the total acid component can be a component derived from the dicarboxylic acid exemplified above other than the terephthalic acid component or the 2,6-naphthalenedicarboxylic acid component, respectively. It can also be a component derived from an aliphatic dicarboxylic acid such as acid or sebacic acid; an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. Further, 20 mol% or less of the total glycol component can be components derived from the glycols exemplified above other than the ethylene glycol component, and for example, hydroquinone, resorcin, 2,2-bis (4-hydroxyphenyl) ) An aromatic diol such as propane; an aliphatic diol having an aromatic ring such as 1,4-dihydroxydimethylbenzene; a polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. It can also be a derived component. Further, for example, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid or an aliphatic oxyacid such as ω-hydroxycaproic acid is used in an amount of 20 mol% based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component. You may copolymerize below. Further, the polyester has an amount in a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component, and a tri- or higher functional polycarboxylic acid or polyhydroxy compound such as trimellitic acid, pentane. Those obtained by copolymerizing erythritol and the like are also included.

  The polyester is known per se and can be produced by a method known per se. The polyester preferably has an intrinsic viscosity of 0.4 to 0.9 dL / g determined by measuring at 35 ° C. as a solution in o-chlorophenol, more preferably 0.5 to 0.7 dL / g. 0.55 to 0.65 dL / g is particularly preferable.

  The base film in the present invention has organic and inorganic fine particles having an average particle size of about 0.01 to 25 μm, preferably about 0.01 to 2 μm, as a lubricant in order to improve the slipping property of the film. For example, the content can be 0.005 to 2% by mass, preferably 0.05 to 0.5% by mass, based on the mass of the film.

  Specific examples of such fine particles include inorganic particles such as calcium carbonate, kaolin, silicon oxide, and barium sulfate, and organic particles such as crosslinked polystyrene resin particles, crosslinked silicone resin particles, and crosslinked acrylic resin particles. Furthermore, fine unevenness may be formed on the film surface by precipitating fine particles from the catalyst residue used in the polyester synthesis reaction, and the film may have good sliding properties.

  In the present invention, these fine particles are preferably subjected to particle size adjustment and coarse particle removal using a purification process before being added to the thermoplastic resin. Examples of the industrial means of the purification process include a dry or wet centrifugal method and an air classification method. In addition, it is particularly preferable that these means are used in combination of two or more and purified stepwise.

  The base film in the present invention can be produced by a conventionally known method. For example, in the present invention, a polyester film is preferable from the viewpoint of mechanical properties, and in particular, a biaxially oriented polyester film is preferable, but such a biaxially oriented polyester film is melted in an extruder after drying the polyester, By extruding from a die (for example, T-die, I-die, etc.) onto a rotating cooling drum, rapidly cooling to an unstretched film, then stretching the unstretched film in a biaxial direction, and heat-fixing as necessary Can be manufactured. In such biaxial stretching, a sequential biaxial stretching method or a simultaneous biaxial stretching method may be used.

  The thickness of the base film can be appropriately set in consideration of ease of application to the intended purpose of the present invention, such as mechanical properties and handleability. From this viewpoint, 5 to 250 μm is preferable, 10 to 80 μm is more preferable, and 20 to 50 μm is further preferable.

  In addition to the above fine particles, the base film may include a colorant, an antistatic agent, an antioxidant, an ultraviolet absorber, a lubricant, a catalyst, and, in the case of a polyester film, polyethylene, polypropylene, ethylene / propylene copolymer. Other resins such as polymers and olefinic ionomers can be optionally contained within the range not impairing the object of the present invention.

[Release layer]
The release layer of the present invention is not particularly limited as long as it satisfies the surface hardness on the surface of the release layer described above. For example, in the silicone resin release layer, the crosslinkable functional group ratio is adjusted, or 3 Use a cross-linking agent such as a functional or tetrafunctional silicon compound, or tighten the curing conditions so that the cross-linking density of the release layer is within the above range. Adjust it. The trifunctional or tetrafunctional silicon compound mentioned here can form not only a silicon compound capable of forming three or four silanol groups by hydrolysis but also a polysiloxane compound formed by a condensation reaction. It may be a thing.

  Furthermore, the release layer of the present invention preferably has the above-mentioned surface resistivity in addition to the surface hardness. Examples of such a release layer include a silanol group for exhibiting antistatic properties. A silicon oxide film which has a three-dimensional siloxane network and has a preferable structure can be mentioned. Such a silicon oxide film can be formed by, for example, hydrolysis and / or condensation reaction of a tetrafunctional silicon compound.

Examples of the tetrafunctional silicon compound preferably used include chloropolysiloxanes such as (Cl ₂ SiO) _n , alkoxysilanes, and alkoxypolysiloxanes. These silicon compounds are preferably hydrolyzed by acting on water before coating, and in particular, a partial hydrolyzate in which 80% or more of side chains and terminal groups are substituted with hydroxyl groups is preferred.

  The hydrolysis and condensation reaction of the tetrafunctional silicon compound can be explained by, for example, alkoxysilane. First, the alkoxy group is hydrolyzed under mild reaction conditions to form a silanol group, and then the dehydration condensation reaction between the silanol groups. A siloxane bond is formed to form a glassy film of silicon oxide having a three-dimensional structure. At this time, since some silanol groups are left behind from the dehydration condensation reaction, the surface resistivity can be easily within the above range. This reaction proceeds sufficiently at room temperature to a temperature of 140 ° C. or less, and the reaction product becomes glassy. Since the reaction by-products are water and alcohol, there is no residue.

When a partial hydrolyzate of a tetrafunctional silicon compound is applied to the film surface, as can be understood from the above, it cures under the influence of temperature and humidity, adheres firmly to the film, and itself has excellent antistatic properties. It will have.
The tetrafunctional silicon compound and / or a partial hydrolyzate thereof as described above can be obtained from the market, and examples thereof include Colcoat EC920, Colcoat EC851, Colcoat P, Colcoat N-103X, Colcoat PX and the like. .

(Thickness)
The thickness of the release layer is preferably in the range of 0.01 to 3 μm, more preferably 0.05 to 2.5 μm, particularly preferably 0.05 to 1.5 μm, and most preferably 0.05 to 1.1 μm. is there. When the thickness is too thin, it becomes a thin layer, so that it is difficult to form a uniform coating film, and a peeling failure tends to occur. On the other hand, when the thickness is too thick, the hardness of the release layer tends to decrease. Further, when thickly applied, the release layer tends to be lost, and the release layer tends to be mixed into the anisotropic conductive film. In addition, the release layer tends to have flexibility, and partial adhesion called blocking is likely to occur when wound up as a film roll.

[Method of forming release layer]
In the present invention, a coating liquid for forming a release layer (hereinafter sometimes referred to as a release layer coating liquid) is applied to the surface of the base film on which the release layer is to be formed. By drying and curing, a release layer can be formed on at least one surface of the base film. Moreover, in order to express the above-mentioned antistatic function, as long as the object of the present invention is not impaired, the antistatic layer may be applied and then a release layer may be applied to form a multilayer.

Hereinafter, a method for forming a release layer will be described by taking as an example a case where the release layer is a silicon oxide film formed by hydrolysis and / or condensation reaction of a tetrafunctional silicon compound, which is a preferred embodiment.
The release layer coating solution comprises, for example, tetraalkoxysilane and / or a partial hydrolyzate thereof, and a diluting solvent. Generally, the ease of adjusting the thickness of the release layer is improved by adjusting the coating solution concentration with a diluting solvent.

As an organic solvent used as a diluting solvent, generally an alcohol type (eg, ethanol, isobutyl alcohol), a ketone type organic solvent (eg, acetone, methyl ethyl ketone (MEK)), a linear hydrocarbon type organic solvent, or an aromatic type organic solvent. In order to dissolve in organic solvents such as solvents (for example, toluene), ether organic solvents and ester organic solvents, these organic solvents are preferably used. Particularly preferred is a mixed solvent of ethanol and MEK.
As a coating method of the release layer coating liquid, any known coating method can be employed, and examples thereof include a roll coater method, a blade coater method, and the like. It may be a coating and is not particularly limited.

  After the release layer coating liquid is applied to the base film, the temperature is preferably 130 ° C. or higher, preferably 180 ° C. or lower, more preferably 160 ° C. or lower, preferably 20 seconds or longer, more preferably 30 seconds. In addition, the release layer is formed by drying and curing in 120 seconds or less, more preferably in 90 seconds or less, and still more preferably in 60 seconds or less. In the present invention, by adopting such drying / curing conditions, the hardness of the surface of the release layer can be within the above range. Moreover, you may irradiate an ultraviolet-ray, an electron beam, etc. as needed for the purpose of hardening.

[Anchor layer]
In this invention, in order to improve the adhesiveness between a base film and a release layer, it is preferable to provide an anchor coat layer between these. Thereby, it can suppress that a release layer mixes in an anisotropic conductive film.
As such an anchor coat layer, an anchor coat layer made of a silane coupling agent can be preferably used. Examples of the silane coupling agent include those represented by the general formula Y—Si—X ₃ . Here, Y is an organic group having a functional group represented by an amino group, an epoxy group, a vinyl group, a methacryl group or a mercapto group, and X represents a hydrolyzable functional group represented by an alkoxy group. The thickness of the anchor coat layer is suitably from 0.01 to 5 μm, particularly from 0.02 to 2 μm from the viewpoint of adhesiveness.

  In forming such an anchor coat layer, there is no particular limitation, but it is applied to the film surface at the stage before biaxial stretching in the film forming process for forming the base film by biaxial stretching, followed by drying and heat treatment. At the same time, it is preferable to employ a so-called in-line coating method in which biaxial stretching is completed.

  Hereinafter, the present invention will be further described by examples. Each characteristic value was measured by the following method.

(1) Surface hardness It measured using the microhardness meter (Elionix FE-1100) in the mold release layer surface of a mold release film sample. As the conditions, a triangular pyramid diamond indenter was used, and the amount of deformation of the release layer at a load of 80 mgf was measured at 27 ° C., and the plastic deformation hardness and elastic deformation hardness were calculated.

(2) Peeling force An epoxy tape (Teraoka Seisakusho: No. 5150) having a width of 25 mm was prepared and bonded to the release layer surface of the release film sample under the conditions of 100 ° C., 0.05 MPa, 30 seconds, A sample for measuring peel force was prepared.
Using such a sample, the peeling force (g / 25 mm) at the interface between the release layer and the epoxy tape was measured with an Instron type tensile tester. At this time, the peeling angle was 180 ° and the peeling speed was 300 mm / min. Five samples were measured, and the average value of these was taken as the room temperature peel force.
In addition, using the sample for measuring peel force obtained above, immediately after applying heat at 80 ° C. for 30 seconds on a heating plate, the peel force (g / 25 mm) was measured in the same manner as described above, and heat peel was performed. Power.

(3) Surface resistivity The surface resistivity of the release layer surface was measured with a measuring instrument (R8340 / R12704) manufactured by Advantest Corporation. The measurement environment was a sample film which was aged for 24 hours in an atmosphere having a temperature of 23 ° C. and a relative humidity of 55% RH, and was measured with the above apparatus. Measurements were taken for any five points and averaged.

[Example 1]
(Manufacture of base film)
Manganese acetate is used as a transesterification catalyst, phosphorous acid is used as a stabilizer, antimony trioxide is used as a polymerization catalyst, and 0.06% by mass of silicon oxide particles (average particle size: 1.8 μm) is used as a lubricant. The intrinsic viscosity is 0.56 dL / g (o-chlorophenol solvent, 25 ° C.), dried polyethylene terephthalate pellets, melted at a melting temperature of 280-300 ° C., extruded from a slit die onto a rotary cooling drum having a surface temperature of 20 ° C., and had a thickness of about 520 μm. An unstretched film was obtained. The obtained unstretched film is preheated to a temperature of 75 ° C., and then heated by an IR heater having a surface temperature of 800 ° C. from above 15 mm between low-speed and high-speed rolls in the longitudinal direction (the film forming machine axis direction). The film is stretched at a magnification of 3.6 times, rapidly cooled, then supplied to a transverse stretching machine, and at a temperature of 120 ° C., the magnification is 3 in the transverse direction (the direction perpendicular to the film forming machine axis direction and the thickness direction). Stretched 9 times. The obtained biaxially oriented film was heat-set at a temperature of 230 ° C. for 5 seconds to obtain a heat-fixed biaxially oriented polyester film having a thickness of 38 μm. In the film forming step, a 3% by mass aqueous solution of 3-glycidoxypropyltrimethoxysilane is used as an anchor coat layer on one side of the film at a position immediately before the uniaxially stretched film that has been longitudinally stretched enters transverse stretching. (Those containing 10 parts by weight of a nonionic surfactant with respect to 100 parts by weight of 3-glycidoxypropyltrimethoxysilane) were applied at a coating amount of 5 g / m ² (wet).

(Preparation of release layer coating solution 1)
A hydrolyzate of polysiloxane (manufactured by Colcoat Co., Ltd .: Colcoat PX) was diluted with isopropyl alcohol (IPA) to prepare a solution having a solid content of 1.5% by mass, and a release layer coating solution 1 was prepared.
This release layer coating solution is applied to the polyester film obtained above (on the anchor coat layer) by a conventional roll coat and dried at a drying temperature of 130 ° C. for 30 seconds. The dry coating thickness is 1.1 μm. A release layer was formed to obtain a release film. The properties of the obtained release film are shown in Table 1.

[Example 2]
A release film was obtained in the same manner as in Example 1 except that the thickness of the release layer was 0.1 μm. The evaluation results are shown in Table 1.

[Example 3]
A release film was obtained in the same manner as in Example 1 except that the release layer coating solution was changed to the following release layer coating solution 2 and the thickness of the release layer was as shown in Table 1. The evaluation results are shown in Table 1.
(Preparation of release layer coating solution 2)
Silicone based on polydimethylsiloxane (manufactured by Toray Dow Corning: SD-7234) as the main agent is diluted with a mixed solvent composed of 80 parts by mass of methyl ethyl ketone (MEK) and 30 parts by mass of toluene, and the solid content concentration is 10 A release layer coating solution 2 was prepared by preparing a mass% solution and adding 2 parts by mass of SRX-212 (manufactured by Toray Dow Corning) as a catalyst to 100 parts by mass of the main agent and mixing.

[Example 4]
A release film was obtained in the same manner as in Example 1 except that the release layer coating solution was changed to the following release layer coating solution 3 and the thickness of the release layer was as shown in Table 1. The evaluation results are shown in Table 1.
(Preparation of release layer coating solution 3)
Silicone based on polydimethylsiloxane (manufactured by Toray Dow Corning: BY24-312) as the main agent is used and diluted with a mixed solvent of 80 parts by mass of methyl ethyl ketone (MEK) and 20 parts by mass of toluene to obtain a solid content concentration of 10 A 2% by mass solution of SRX-212 (manufactured by Toray Dow Corning Co., Ltd.) as a catalyst was added to 100 parts by mass of the main agent to prepare a release layer coating solution 3.

[Comparative Example 1]
A release film was obtained in the same manner as in Example 1 except that the release layer coating solution was changed to the following release layer coating solution 4 and the thickness of the release layer was as shown in Table 1. The evaluation results are shown in Table 1.
(Preparation of release layer coating solution 4)
Using pure water as a solvent, 2.5 parts by mass of an acrylic binder (manufactured by Toa Gosei Co., Ltd .: N-31-4) as a main agent, 0.2 parts by mass of a surfactant (manufactured by Kao Co., Ltd .: Lionol LL950), a long chain in the side chain Polyvinyl alcohol-based mold release agent having one alkyl group (manufactured by Yushi Kogyo Co., Ltd .: Pyroyl 406) is mixed with 0.7 part by mass, and a release layer coating is applied at a solid content concentration of 10% by mass using pure water as a diluent solvent. Solution 4 was adjusted.

[Comparative Example 2]
A release film was obtained in the same manner as in Example 1 except that the release layer coating solution was changed to the following release layer coating solution 4. The evaluation results are shown in Table 1.
(Preparation of release layer coating solution 5)
A toluene solvent was mixed at a ratio of 95 parts by mass of SFC329 (polyester-melamine, manufactured by DIC) and 5 parts by mass of SP hardener B (acid catalyst, manufactured by DIC), and the solid content concentration was adjusted using pure water as a diluent solvent. The release layer coating solution 5 was adjusted to 5% by mass.
In addition, the normal temperature peeling of Comparative Example 2 was regarded as “no data” (−) because the epoxy tape pressure-sensitive adhesive was transferred to the release film and it was difficult to peel the interface between the release layer and the pressure-sensitive adhesive layer.

  In the release film of the present invention, fluctuations due to temperature changes in the peeling force between the anisotropic conductive film and the carrier film after the temporary bonding step are suppressed, so peeling in the carrier film peeling step before entering the main bonding step Can be carried out stably and can be suitably used as a release film for anisotropic conductive films.

Claims (3)

A release film having a release layer on at least one surface of a base film, the plastic deformation hardness obtained by a microhardness meter on the release layer surface is 20 mgf / μm ² or more, and the elastic deformation hardness is 400 mgf / μm. ^A release film for anisotropic conductive film, which is ² or more.   The release film for anisotropic conductive films according to claim 1, wherein the release layer is a silicon oxide film formed by hydrolysis and / or condensation reaction of a tetrafunctional silicon compound. The release film for anisotropic conductive films according to claim 1 or 2, wherein the surface specific resistance on the surface of the release layer is 10 ⁵ to 10 ¹¹ Ω / □.